A high-speed LVDS signal over copper (either cable or traces) has a distance length limitation, which varies with the cable type and quality, for correctly transmitting and receiving PCIe signals. Two methods exist for increasing this distance. The first is to use a higher quality cable, but this method still has an upper limit because of resistance in the copper wires, inherent inductance, and other physical properties of the copper/metal medium over which the signals are being sent. The second method is to use a PCIe buffer periodically in the path of the signal. This buffer can be placed at either end, both, or in the middle of the path. Again, once the path has reached a critical length, another buffer must be used. The downfall to this method is the high cost and the required physical placement of this buffer periodically in the path.
For a (copper) cabled solution such as what Magma, Inc. of San Diego, Calif., designs and sells, it is not feasible to put buffers in the middle of a cable. This would introduce many EMI/EMC and signal integrity problems as well as increased cost.
Two examples of prior art to increase distance are to install a PCIe to giga-bit ethernet card (for a copper interface) or a fiber optic channel card (for an optical interface) on both ends. In each case the giga-bit ethernet or fiber optic channel use an overlay protocol. The overlay protocol has many drawbacks, most importantly, is the overhead latency associated with the addition of a protocol. Because of this latency, one cannot expect full PCIe throughput using this art or method. Thus, currently there is a limit in meters which is achievable using a design methodology that does not add latency.